Unpowered gear shifting control method and system of HMCVT gearbox and motor vehicle

Abstract

The invention relates to an unpowered gear shifting control method and system of an HMCVT gearbox and a motor vehicle. In the torque exchange stage under the unpowered gear shifting working condition, a change-in clutch keeps the Kiss Point point pressure, meanwhile, the speed difference between the two ends of the change-in clutch is kept within the set range, and the speed difference serves as the transverse axis x axis for inquiring a dynamic pressure curve; and waiting for set time, gradually reducing the speed difference by adjusting the displacement of the hydraulic unit during the period, and when the speed difference at the two ends of the switching clutch is smaller than a set value delta n, determining the combination pressure of the switching clutch according to the part with the speed difference smaller than delta n, controlling the switching clutch to be closed, and completing power transmission switching. Accurate adaptation is achieved by taking the speed difference as a dynamic control reference, hydraulic speed regulation and clutch pressing are processed in stages, and system oscillation caused by simultaneous regulation of multiple variables is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of engine control, and particularly to a power-off shifting control method, system and motor vehicle for an HMCVT transmission. Background Art

[0002] The statements in this part only provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] For an HMCVT transmission, i.e., a Hydraulic Mechanical Continuously Variable Transmission, two clutches are required for power exchange during downshifting. If the KissPoint (contact point, referring to the moment when the clutch friction plates just come into contact and start to transmit torque, at this time the clutch is neither fully engaged nor fully disengaged) of the engaged clutch is not appropriate, it will lead to the problem that both clutches participate in power transmission simultaneously during the torque exchange stage, resulting in the vehicle speed decreasing and then accelerating again, causing rapid fluctuations in vehicle speed, accelerating the wear of the clutch, and generating a strong sense of jerk. Summary of the Invention

[0004] In order to solve the technical problems existing in the above background art, the present invention provides a power-off shifting control method, system and motor vehicle for an HMCVT transmission. By making full use of the characteristics of the infinitely variable transmission hydraulic system to adjust the speed ratio, fully considering the engagement pressure of the engaged clutch during power-off shifting, and allowing the engaged clutch to bear power only when the speed difference of the engaged clutch is small, the shifting shock problem caused by inappropriate KissPoint of the engaged clutch is solved.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The first aspect of the present invention provides a power-off shifting control method for an HMCVT transmission, including the following steps:

[0007] During the torque exchange stage under the power-off shifting condition, while maintaining the Kiss Point pressure of the engaged clutch, maintain the speed difference between both ends of the engaged clutch within a set range, and use the speed difference as the horizontal axis x-axis for querying the dynamic pressure curve;

[0008] Wait for a set time. During this period, gradually reduce the speed difference by adjusting the displacement of the hydraulic unit. When the speed difference between both ends of the engaged clutch is less than the set value Δn, determine the engagement pressure of the engaged clutch according to the part where the speed difference is less than Δn, and control the engaged clutch to close to complete the power transmission switching.

[0009] As a further implementation, according to the changes in vehicle speed and engine speed, it is determined whether it is in a no-power shift condition.

[0010] As a further implementation, if it is not less than the set value Δn, the displacement of the hydraulic unit is continuously adjusted.

[0011] As a further implementation, through closed-loop control, the speed difference between the two ends of the engaged clutch is maintained within the set range, and the dynamic pressure curve is queried with this as the initial value.

[0012] As a further implementation, after obtaining the engagement pressure of the engaged clutch by querying the dynamic pressure curve, without engaging the torque value for power transmission, by waiting for the set time, the displacement of the hydraulic unit is adjusted to gradually reduce the speed difference.

[0013] As a further implementation, after the speed difference is reduced through the adjustment of the displacement of the hydraulic unit, the part less than Δn is the remaining speed difference.

[0014] As a further implementation, the remaining speed difference is used to obtain the engagement pressure of the engaged clutch by querying the dynamic pressure curve.

[0015] As a further implementation, the dynamic pressure curve is obtained in advance through experimental or simulation methods.

[0016] The second aspect of the present invention provides a no-power shift control system for an HMCVT transmission, including:

[0017] A first control unit, configured to: during the torque exchange stage in the no-power shift condition, while maintaining the pressure at the Kiss Point of the engaged clutch, maintain the speed difference between the two ends of the engaged clutch within the set range, and use the speed difference as the horizontal axis x-axis for querying the dynamic pressure curve;

[0018] A second control unit, configured to: wait for the set time, during which the speed difference is gradually reduced by adjusting the displacement of the hydraulic unit, and when the speed difference between the two ends of the engaged clutch is less than the set value Δn, determine the engagement pressure of the engaged clutch according to the part of the speed difference less than Δn, and control the engaged clutch to close to complete the power transmission switch.

[0019] The third aspect of the present invention provides a motor vehicle, which has an on-vehicle computer, and the on-vehicle computer executes the steps in the above-mentioned no-power shift control method for an HMCVT transmission.

[0020] Compared with the prior art, the above one or more technical solutions have the following beneficial effects:

[0021] 1. By making full use of the characteristics of the hydraulic system of the continuously variable transmission to adjust the speed ratio, the pressure of the shift-in clutch is fully considered under no-power shifting, and the shift-in clutch is allowed to take on the power only when the speed difference of the shift-in clutch is small, thus solving the shift shock problem caused by inappropriate kiss point of the shift-in clutch.

[0022] 2. Transform the speed difference from a "suppressed parameter" to a "reference axis of the control process" to achieve precise adaptation. At the same time, the hydraulic speed regulation and clutch clamping are handled in stages to avoid system oscillation caused by adjusting multiple variables at the same time.

[0023] 3. It can realize gear shifting control on the existing mechanical structure without adding additional sensors, maintain the continuity of power transmission during the entire deceleration process, reduce the problem of vehicle speed inconsistency caused by gear shifting, and can quickly tighten to ensure the power transmission ratio and ensure the smoothness of power transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 It is a schematic diagram of the unpowered shift control process of the HMCVT transmission provided by one or more embodiments of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0027] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0029] Terminology explanation:

[0030] The no-power shift condition means that during the shifting process, the power transmitted from the engine to the transmission is temporarily interrupted, thus achieving smooth gear shifting. Specifically: during shifting, by controlling the separation and engagement of the clutch, the power of the engine is temporarily not transmitted to the output shaft, thereby achieving a shift without power interruption.

[0031] The HMCVT transmission achieves stepless speed change through the coordinated operation of hydraulic and mechanical paths, and requires the alternating operation of two clutches (the current gear clutch Clutch A and the target gear clutch Clutch B) during shifting. Among them:

[0032] Clutch A (current gear): Responsible for transmitting the power of the current gear (such as high gear).

[0033] Clutch B (target gear): Prepare to engage the power of the target gear (such as low gear).

[0034] During downshifting, Clutch A gradually releases and Clutch B gradually engages, and the two achieve continuous power transmission through overlapping control.

[0035] At the initial stage of shifting, the Kiss Point (contact point) of Clutch A needs to be precisely controlled so that while the transmitted torque gradually decreases, Clutch B starts to contact and transmit torque. The Kiss Point of Clutch B needs to be synchronized with the separation of Clutch A to ensure a smooth transition of power from Clutch A to Clutch B and avoid power interruption or overlap.

[0036] The clutch pressure is adjusted through the hydraulic system to make the slip friction state (semi-linkage) of the two clutches strictly match in terms of time, torque, and speed, thereby achieving power exchange.

[0037] If the Kiss Point is not properly controlled (such as too early or too late), it will cause the "overlap area" where the two clutches transmit power simultaneously to be too long or too short. The specific impacts are as follows:

[0038] Power path conflict: When Clutch A is not fully separated while Clutch B is already engaged, the two clutches will transmit torque simultaneously, resulting in power being transmitted to the output shaft through two mechanical paths.

[0039] At this time, due to the different transmission ratios of the two paths (such as high gear and low gear), an internal power circulation will occur, that is, part of the power is "self-cancelled" by the mechanical structure, resulting in unstable power output of the whole vehicle.

[0040] Vehicle speed fluctuation phenomenon: During the deceleration phase, Clutch A is still transmitting high-speed gear power, but Clutch B has a higher low-speed gear ratio (greater torque), resulting in a sudden increase in engine load and a brief drop in vehicle speed.

[0041] When Clutch B is fully engaged, the high torque of the low gear is released instantly, and the vehicle speed suddenly increases. This rapid switching of "deceleration-acceleration" causes the vehicle speed to fluctuate violently, and the driver feels a distinct sense of jerk.

[0042] If the two clutches stay in the Kiss Point area for too long, the friction plates will generate high temperature and wear due to long-term semi-clutch.

[0043] At the same time, power path conflicts will cause the clutch to be subjected to alternating torque, and the friction plate surface is prone to uneven wear, shortening the life of the clutch.

[0044] At the same time, power path conflicts can cause sudden changes in engine load, forcing the ECU to frequently adjust the injection volume and throttle opening, further exacerbating vehicle speed fluctuations. In addition, clutch pressure fluctuations can cause delayed response in the hydraulic system, forming a vicious cycle.

[0045] Therefore, the following embodiments provide a non-powered shifting control method, system and motor vehicle for an HMCVT transmission, which fully utilizes the characteristics of the hydraulic system of the continuously variable transmission for adjusting the speed ratio, fully considers the acceptance pressure of the shift-in clutch under non-powered shifting, and allows the shift-in clutch to accept power only when the speed difference of the shift-in clutch is small, thereby solving the shifting shock problem caused by an inappropriate kiss point of the shift-in clutch.

[0046] Embodiment 1:

[0047] Taking high-horsepower tractors as an example, the shift points of the HMCVT gearbox used in high-horsepower tractors are discontinuous when the C2 and C1 clutches are switched. It is necessary to eliminate the speed difference at both ends of the clutch by adjusting the displacement of the hydraulic unit.

[0048] In the case of non-powered shifting, the shifting clutch will exchange power before adjusting the displacement of the hydraulic unit. During this process, the clutch kiss point is too large, which makes the pressure of the C1 clutch too large, causing the C1 clutch to intervene in the transmission power in advance. At this time, the hydraulic unit speed ratio is not appropriate, resulting in different clutches intervening in the transmission system. The speed transmitted is inconsistent, which in turn causes a rapid change in vehicle speed.

[0049] In order to avoid this situation, the present embodiment effectively avoids the conflict between the two clutches in transmitting power and avoids the clutch from transmitting power at an inappropriate speed ratio.

[0050] In this embodiment, the no-power shift condition is calculated. Under this condition, during the torque exchange stage of the shift, the pressure at the kiss point of the engaged clutch is maintained, and at the same time, the speed difference at the engaged clutch end is frozen. This is used as the horizontal axis for querying the dynamic pressure curve because the initial values of the speed differences at different speeds are also inconsistent.

[0051] At the same time, it does not directly cut into the torque value for power transmission. Instead, it waits for a period of time and first adjusts the speed of the hydraulic unit. In the middle and late stages of the hydraulic unit speed adjustment, the clutch is tightened according to the speed difference between the two ends of the engaged clutch, ensuring that the speed difference between the two ends of the engaged clutch is not large during the power transmission process. This can not only quickly tighten to ensure the power transmission ratio but also ensure the smoothness of power transmission.

[0052] A no-power shift control method for an HMCVT transmission includes the following steps:

[0053] During the torque exchange stage in the no-power shift condition, while the engaged clutch maintains the pressure at the Kiss Point, the speed difference between the two ends of the engaged clutch is maintained within a set range, and the speed difference is used as the horizontal axis (x-axis) for querying the dynamic pressure curve.

[0054] Wait for a set time. During this period, the speed difference is gradually reduced by adjusting the displacement of the hydraulic unit. When the speed difference between the two ends of the engaged clutch is less than the set value Δn, the engagement pressure of the engaged clutch is determined based on the part of the speed difference less than Δn, and the engaged clutch is controlled to close to complete the power transmission switch.

[0055] As a further implementation, it is determined whether it is in the no-power shift condition according to the changes in vehicle speed and engine speed.

[0056] As a further implementation, if it is not less than the set value Δn, the displacement of the hydraulic unit is continuously adjusted.

[0057] As a further implementation, through closed-loop control, the speed difference between the two ends of the engaged clutch is maintained within a set range, and this is used as the initial value for querying the dynamic pressure curve.

[0058] As a further implementation, after obtaining the engagement pressure of the engaged clutch by querying the dynamic pressure curve, it does not cut into the torque value for power transmission. By waiting for a set time, the displacement of the hydraulic unit is adjusted to gradually reduce the speed difference.

[0059] As a further implementation, after the speed difference is reduced through the adjustment of the hydraulic unit displacement, the part less than Δn is the remaining speed difference.

[0060] As a further implementation, the remaining speed difference is used to obtain the engagement pressure of the engaged clutch by querying the dynamic pressure curve.

[0061] As a further implementation, the dynamic pressure curve is obtained in advance through experimental or simulation methods.

[0062] Combined with Figure 1 Shown in the flowchart, the powertrain-free shift control method of the HMCVT transmission proposed in this embodiment is further introduced.

[0063] As a further implementation, according to the changes in vehicle speed and engine speed, it is judged whether the current is in a powertrain-free shift condition. If so, proceed to the next step; if not, end.

[0064] As a further implementation, during the torque exchange stage under the powertrain-free shift condition, while the engaged clutch maintains the pressure at the kiss point, the speed difference across the engaged clutch is maintained within a set range (i.e., "frozen" the speed difference across the engaged clutch), and the speed difference is used as the horizontal axis x of the query dynamic pressure curve (the initial values of the speed difference are inconsistent at different speeds), to obtain the engagement pressure of the engaged clutch.

[0065] As a further implementation, after obtaining the engagement pressure of the engaged clutch, instead of directly switching to the torque value for power transmission, wait for a set time, during which the speed difference is gradually reduced by adjusting the displacement of the hydraulic unit.

[0066] As a further implementation, when the engaged clutch maintains the pressure at the kiss point, it is judged whether the speed difference across the engaged clutch is less than the set value Δn; specifically:

[0067] If it is not less than the set value Δn, return to the previous step to continue adjusting the displacement of the hydraulic unit;

[0068] If it is less than the set value Δn (generally in the middle and late stages of the displacement adjustment of the hydraulic unit), then determine the engagement pressure of the engaged clutch according to the remaining speed difference (i.e., the part of the speed difference that is less than Δn after being reduced by the displacement adjustment of the hydraulic unit), and control the engaged clutch to close to complete the power transmission switch.

[0069] The above shift control method can achieve shift control without adding additional sensors on the existing mechanical structure, can maintain the coherence of power transmission during the entire deceleration process, reduce the problem of inconsistent vehicle speed caused by shifting, and can not only quickly compress to ensure the power transmission ratio but also ensure the smoothness of the transmitted power.

[0070] Kiss point pressure maintenance: At the initial stage of torque exchange, the engaged clutch maintains the "kiss point" pressure (critical contact pressure), making the clutch in a "semi-engaged" state, neither transmitting large torque nor gradually synchronizing the speeds at both ends through frictional contact.

[0071] Differential speed freezing: The differential speed at both ends of the clutch can be dynamically stabilized at the initial value through closed-loop control (such as PID to adjust the hydraulic pressure or adjust the engine torque output), avoiding shock or power interruption caused by the expansion of the differential speed.

[0072] The horizontal axis of the pressure curve is bound to the differential speed: The differential speed at both ends of the clutch is used as the core parameter for dynamically adjusting the hydraulic pressure. According to different initial differential speeds, the corresponding pressure curves are matched in real time (for example: a higher pressure gradient is used when the differential speed is large, and a gentle pressure gradient is used when the differential speed is small), and the pressure curves themselves can be obtained in advance through experiments, simulation, etc.

[0073] Adapting to different working conditions: Avoiding overpressure or underpressure problems caused by fixed pressure curves and adapting to the shifting requirements under different speeds and loads.

[0074] Delayed power transmission: During the differential speed freezing stage, the power torque is not directly transmitted, but the input / output end speeds are actively adjusted through the hydraulic system to gradually reduce the differential speed (for example: adjusting the displacement or oil pressure of the hydraulic pump / motor).

[0075] Mid-late stage differential speed closed-loop control: In the later stage of hydraulic speed regulation (when the differential speed has been significantly reduced), the clutch clamping force is adjusted in real time according to the remaining differential speed to ensure that the differential speed approaches zero at the final engagement, realizing shock-free power transmission.

[0076] Rapidity: By differential speed freezing and dynamic pressure adjustment, the time of the hydraulic speed regulation stage is shortened, avoiding the delay in the traditional method of engaging after complete synchronization.

[0077] Smoothness: Using hydraulic speed regulation and differential speed closed-loop control to ensure that the speeds at both ends are sufficiently close when the clutch engages, eliminating jerks or shocks in power transmission.

[0078] The shifting control method of this embodiment uses the differential speed as the dynamic control benchmark, that is, transforms the differential speed from a "suppressed parameter" to a "reference axis of the control process" to achieve precise adaptation. At the same time, it realizes staged decoupled control, that is, processes the hydraulic speed regulation and clutch clamping in stages to avoid system oscillation caused by simultaneously adjusting multiple variables.

[0079] Embodiment 2:

[0080] The second aspect of the present invention provides a power-off shifting control system for an HMCVT transmission, including:

[0081] The first control unit is configured to: during the torque exchange stage in the power-off shifting condition, while maintaining the pressure at the Kiss Point of the engaged clutch, maintain the differential speed at both ends of the engaged clutch within a set range, and use the differential speed as the horizontal axis x-axis for querying the dynamic pressure curve;

[0082] The second control unit is configured to: wait for a set time, during which the speed difference is gradually reduced by adjusting the displacement of the hydraulic unit. When the speed difference between the two ends of the engaged clutch is less than the set value Δn, determine the engagement pressure of the engaged clutch according to the part of the speed difference less than Δn, control the engaged clutch to close, and complete the power transmission switch.

[0083] By making full use of the characteristics of the continuously variable transmission hydraulic system to adjust the speed ratio, fully considering the bearing pressure of the engaged clutch during power-off shifting, and allowing the engaged clutch to bear power only when the speed difference of the engaged clutch is small, the problem of shifting shock caused by inappropriate kiss point of the engaged clutch is solved.

[0084] The speed difference is changed from "a suppressed parameter" to "a reference axis of the control process" to achieve precise adaptation. At the same time, the hydraulic speed regulation and the clutch pressing are processed in stages to avoid system oscillation caused by adjusting multiple variables simultaneously.

[0085] It can achieve shift control on the existing mechanical structure without adding additional sensors, can maintain the coherence of power transmission during the entire deceleration process, reduce the problem of discontinuous vehicle speed caused by shifting, and can quickly press to ensure the power transmission ratio and the smoothness of the transmitted power.

[0086] Embodiment III:

[0087] A motor vehicle has an on-vehicle computer, and the on-vehicle computer executes the steps in the power-off shifting control method of the above HMCVT transmission.

[0088] During the torque exchange stage under the power-off shifting condition, while maintaining the pressure at the Kiss Point of the engaged clutch, the speed difference between the two ends of the engaged clutch is maintained within the set range, and the speed difference is used as the horizontal axis x-axis for querying the dynamic pressure curve;

[0089] Wait for a set time, during which the speed difference is gradually reduced by adjusting the displacement of the hydraulic unit. When the speed difference between the two ends of the engaged clutch is less than the set value Δn, determine the engagement pressure of the engaged clutch according to the part of the speed difference less than Δn, control the engaged clutch to close, and complete the power transmission switch.

[0090] By making full use of the characteristics of the continuously variable transmission hydraulic system to adjust the speed ratio, fully considering the bearing pressure of the engaged clutch during power-off shifting, and allowing the engaged clutch to bear power only when the speed difference of the engaged clutch is small, the problem of shifting shock caused by inappropriate kiss point of the engaged clutch is solved.

[0091] The speed difference is changed from "a suppressed parameter" to "a reference axis of the control process" to achieve precise adaptation. At the same time, the hydraulic speed regulation and the clutch pressing are processed in stages to avoid system oscillation caused by adjusting multiple variables simultaneously.

[0092] It can achieve shift control on the existing mechanical structure without adding extra sensors, maintain the coherence of power transmission during the entire deceleration process, reduce the problem of discontinuous vehicle speed caused by shifting, quickly tighten to ensure the power transmission ratio, and ensure the smoothness of transmitted power.

[0093] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. The non-powered shift control method of the HMCVT transmission is characterized in that: The following steps are involved: In the torque exchange stage under the non-powered shifting condition, the shift-in clutch maintains the Kiss Point pressure while keeping the speed difference between the two ends of the shift-in clutch within the set range, and the speed difference is used as the horizontal axis x-axis for querying the dynamic pressure curve; Wait for the set time, during which the speed difference is gradually reduced by adjusting the displacement of the hydraulic unit. When the speed difference at both ends of the clutch is less than the set value Δn, the engagement pressure of the clutch is determined based on the part of the speed difference less than Δn, the clutch is controlled to close, and the power transmission switch is completed.

2. The unpowered shift control method of the HMCVT transmission as claimed in claim 1, characterized in that: Based on the changes in vehicle speed and engine speed, it is determined that the vehicle is in a no-power shifting condition.

3. The non-powered shift control method of the HMCVT transmission as claimed in claim 1, characterized in that: If it is not less than the set value Δn, continue to adjust the hydraulic unit displacement.

4. The non-powered shift control method of the HMCVT transmission as claimed in claim 1, characterized in that: Through closed-loop control, the speed difference between the two ends of the clutch is maintained within the set range, and the dynamic pressure curve is queried using this as the initial value.

5. The unpowered shift control method of the HMCVT transmission as claimed in claim 1, characterized in that: After querying the dynamic pressure curve to obtain the engagement pressure of the clutch, the torque value for transmitting power is not cut in. By waiting for the set time, the displacement of the hydraulic unit is adjusted to gradually reduce the speed difference.

6. The non-powered shift control method of the HMCVT transmission as claimed in claim 1, characterized in that: After the speed difference is reduced by the hydraulic unit displacement adjustment, the part less than Δn is the remaining speed difference.

7. The non-powered shift control method of the HMCVT transmission as claimed in claim 1, characterized in that: The remaining speed difference is obtained by querying the dynamic pressure curve to obtain the engagement pressure of the clutch.

8. The non-powered shift control method of the HMCVT transmission as claimed in claim 1, characterized in that: The dynamic pressure curve is obtained in advance through experiments or simulation methods.

9. The powerless shift control system of the HMCVT gearbox is characterized by: include: The first control unit is configured to: in the torque exchange stage under the non-powered shifting condition, while the shift-in clutch maintains the KissPoint pressure, keep the speed difference at both ends of the shift-in clutch within a set range, and use the speed difference as the horizontal axis x-axis for querying the dynamic pressure curve; The second control unit is configured to: wait for a set time, during which the speed difference is gradually reduced by adjusting the displacement of the hydraulic unit; when the speed difference between the two ends of the clutch is less than the set value Δn, the engagement pressure of the clutch is determined based on the part of the speed difference less than Δn, the clutch is controlled to close, and the power transmission switch is completed.

10. A motor vehicle, characterized in that: A vehicle-mounted computer is provided, and the vehicle-mounted computer executes the steps in the unpowered shift control method of the HMCVT transmission as described in any one of claims 1-8.

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